The current interest in the possible effects of magnetic fields on the brain was originally stimulated by the identification of correlations between some apparently paranormal events (such as hallucinations) and the occurrence of major disturbances to the magnetic field of the earth. Study of the published literature suggests that much of this work is unlikely to yield meaningful or reliable results, primarily because many of the investigators involved seem unaware of a number of salient facts known to physicists, communication engineers (...) or neurologists. Some of these may be rather recondite but are none the less extremely relevant. A few examples are discussed. (shrink)